Field of the Invention
The present invention relates to a zoom lens and an image pickup apparatus including the same, the zoom lens being particularly advantageous as an image pickup optical system for use in an image pickup apparatus such as a digital still camera, a video camera, a monitoring camera, or a broadcasting camera.
Description of the Related Art
As an image pickup optical system for use in an image pickup apparatus, desired is a compact zoom lens having a wide angle of view and a high zoom ratio. The zoom lens is also desired to have a high resolving power. As a zoom lens for achieving a high zoom ratio, a positive-lead type zoom lens is known, which includes, in order from an object side to an image side, first to fourth lens units having positive, negative, positive, and negative refractive powers, respectively, as well as a following rear unit including at least one lens unit.
Japanese Patent Application Publication No. 2012-083601 discloses a zoom lens including first to fifth lens units having positive, negative, positive, negative, and positive refractive powers, respectively. In this zoom lens, the first lens unit is formed of a cemented lens of a negative lens and a positive lens, and the second to fourth lens units move for zooming.
Japanese Patent Application Publication No. 2006-178244 discloses a zoom lens including first to fifth lens units having positive, negative, positive, negative, and positive refractive powers, respectively. In this zoom lens, the first lens unit is formed of a single positive lens, and the second to fifth lens units move for zooming.
Japanese Patent Application Publication No. 2012-47814 discloses a zoom lens including, in order from the object side to the image side, first to sixth lens units having positive, negative, positive, negative, negative, and positive refractive powers, respectively. In this zoom lens, the second, fourth, and fifth lens units move for zooming.
Widening the angle of view of a positive-lead type zoom lens tends to increase the effective diameter of the front lens and thereby enlarge the entire system. Thus, in order to widen the angle of view without sacrificing the compactness of the entire system, it is important to appropriately set the configuration of each lens unit or particularly the first lens unit.
It is also important to appropriately set the refractive powers of the movable lens units, such as the third or fourth lens unit, and the amounts by which these lens units move for zooming.